A. Field of the Invention
The present invention relates to a method and apparatus for displaying digital radiological frames on a computer monitor or other display device. The radiological frames may be from a computed tomography device, a magnetic resonance imaging device, an ultrasound device, a nuclear medicine imaging device or other radiological equipment producing digital radiological frames.
B. Description of the Related Art
Conventional radiological equipment print multiple frames acquired in a radiological study onto one or more sheets of film. Typically, radiological equipment have a video output signal. This video output signal may be used directly to print the multiple radiological frames or may be digitized prior to being forwarded to a printer or other display means.
Regardless of how the sheet of film may have been printed, each sheet of film typically includes more than a single radiological frame. A large portion of each frame is either blank or contains redundant information associated with the images. Because a large portion of each film sheet is blank or contains redundant information, a large number of film sheets are necessary to display a complete radiological study. Thus, a large amount of film is used for each radiological study. The film sheets are expensive and the film costs add to the overall costs of the radiological study itself. Moreover, for a medical provider the overall costs of storing large amounts of film can also be great.
By arranging more frames on a single film sheet, the number of film sheets needed for a particular radiological study can be reduced, thus reducing the costs of a radiological study. More frames can be arranged on a single sheet of film if each radiological frame is proportionally reduced. Proportionally reducing the size of a radiological frame means printing the entire radiological frame in a smaller size. This method of increasing the number of radiological frames printed on a single sheet of film has an important disadvantage. Proportional reduction of radiological frames reduces the size of the medical image displayed on the frame, which reduces the detail available on the image and thereby diminishes the usefulness of the image to the medical practitioner.
In the above referenced related U.S. patent application, a method and apparatus for increasing the number of radiological frames printed on a single sheet of film is disclosed. The claimed method and apparatus does not reduce the size of the medical image and further does not risk eliminating part of the medical image nor is time consuming or operator dependent. Increasingly, however, radiological frames are not printed on film but are displayed on a display screen for viewing by the medical practitioner. The same problems that are present in printing of radiological images are present in displaying the radiological images (i.e., more than one image may be displayed on a single screen and a large portion of the screen is blank or contains redundant information associated with the images while proportionally reducing the size of the radiological frame has distinct disadvantages).
Thus, in the art of teleradiology, more radiological frames have been displayed on a display screen by "cropping" each frame. The term cropping refers to maintaining the medical image size while reducing the physical dimension of each frame by eliminating portions of the frame.
Two methods of cropping are known in the art. Blind cropping involves presetting the frame dimensions without regard to the image displayed on the frame. With manual masking, the operator of the radiological equipment considers each frame and determines manually where the frame will be cropped.
With blind cropping, while the medical image size is maintained, the physical cropped dimensions are preset irregardless of the size or position of the medical image on any particular radiological frame, making it is possible that the entire medical image may not be displayed on a blind cropped frame. Again, the usefulness of the frame, or perhaps entire study, to the medical practitioner may be reduced.
With manual cropping, the medical image size is maintained and an operator controls exactly where each frame will be cropped as it is generated. Manual cropping thus ensures that the medical image size remains large enough to be useful to the medical practitioner and portions of the medical image displayed on the radiological frame are not cropped off. Manual cropping, however, involves intense manual operator input and is thus time consuming and operator dependent.
In light of the foregoing, there is a need for an apparatus and method of increasing the number of radiological frames displayed on a display screen that will not reduce the size of the medical image so as to diminish the usefulness of the medical image and would not risk eliminating part of the medical image nor is time consuming and operator dependent.